Nitrogen generator

ABSTRACT

A material for generating hot nitrogen gas comprising sodium azide and sulfur in the presence of a conventional solid propellant ignitor.

Unite States Patent [1 1 Boyars et a1.

[ NITROGEN GENERATOR [75 I Inventors: Carl Boyars; Carl T. Zovko, bothof Silver Spring, Md.

[73 Assignee: The United States of America, as

represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Oct. 13, 1972 [21] Appl. No.: 297,513

[ NOV. 27, 1973 [56] References Cited UNITED STATES PATENTS 2,981,6164/1961 Boyer 149/35 Primary Examiner-Stephen .l. Lechert, Jr. Att0rneyR.S. Sciascia et a1.

[5 7] ABSTRACT A material for generating hot nitrogen gas comprisingsodium azide and sulfur in the presence of a conventional solidpropellant ignitor.

14 Claims, No Drawings NITROGEN GENERATOR BACKGROUND OF THE INVENTIONThis invention generally relates to a gas generator and moreparticularly to a solid propellant nitrogen gas generator.

Currently nitrogen gas generators find use in the fields of electricpower, mechanical work, pressurization of liquid propellants and as afuel source for gas dynamic lasers. Gas dynamic lasers utilizing gascompositions which are mainly N have been operated by are heating of thegas, which had been stored as a gas under pressure or as a cryogenicliquid or else by the combustion of pre-heated CO with with subsequentaddition of N from the same sources. However, any system of furnishingthe gas composition which depends on pressurized or cryogenic N isundesirably bulky and inconvenient.

Some nitrogen gas generators are based on the reaction of NaN with P ClFN 0 or other similar materials to produce N but use of these toxic,corrosive gases and liquids have proven to be unacceptably hazardous topersonnel.

Thus research has been conducted in an attempt to find a relatively safemethod of producing nitrogen which does not require the use of bulky,inconvenient equipment.

SUMMARY OF THE INVENTION Accordingly one object of this invention is toprovide a new composition for generating nitrogen.

Another object of this invention is to provide a composition forgenerating nitrogen which is not bulky, and inconvenient to use.

A still further object of this invention is to provide a composition forgenerating nitrogen which does not use toxic or corrosive materialswhich are hazardous to personnel.

Yet another object of this invention is to provide a composition forgenerating pure nitrogen which can be used in gas dynamic lasers.

A still further object of this invention is to provide nitrogen whichcan be used in the fields of electrical power, mechanical work andpressurization of liquid propellants.

These and other objects of this invention are accomplished by providinga solid composition comprising sodium azide or an azide of similarsensitivity, and sulfur which are in the presence of a conventionalsolid propellant initiator.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention comprisesa solid composition which is capable of producing hot nitrogen gas. Thiscomposition comprises (1) sodium azide or an azide of similarsensitivity and (2) sulfur which are in the pres ence of any of theconventional solid propellant initiators. If it is desired to have COpresent together with the nitrogen gas, as is the case when N is used ingas dynamic lasers wherein it is desirable for the gas being generatedto comprise about 80-90 percent N -15 percent CO and 1-2 percent water,the CO may be added after N generation or it may be supplied by adding acarbonate or other fuel oxidizer combinations such as carbon and sodiumnitrate to the solid propellant.

Since the azide and sulfur are not hypergolic it is necessary to have aninitiator or ignitor present in the combustion chamberin order to startthe reaction. The reaction is started by buming or otherwise igniting asmall conventional solid propellant ignitor. Once the reaction hasstarted the ignitor is no longer necessary. Once started thestoichiometric reaction between sodium azide and sulfur is ln situationswhere it is desirable to have as few products in addition to N presentin the gas, it is preferred to have about stoichiometric amounts of theazide and sulfur present. However for most uses, it is only necessary tohave some quantity of the fuel and oxidizer present. In practice wherelow combustion temperatures are desirable to minimize impurities in thegas, it is preferable to have the sulfur constituent present in anamount less than stoichiometric, even as low as 20 percent of thestoichiometric quantity, and preferably as low as about percent of thestoichiometric quantity. As will be recognized by those skilled in theart, it is also desirable to have the azide constituent present in anamount no less than 20 percent of the stoichiometric quantity andpreferably as about 75 percent of the stoichiometric quantity.

As can be seen from the above equation, the chemical reaction thatproduces N also produces other products. For some uses, such as gasdynamic laser, these impurities should be removed before the gas entersthe laser, because impurities of this type can plug the nozzle, absorbor scatter light or coat the optical components. The solid and/or liquidimpurities can be removed by any of the conventional techniques such as,for example, by passing the gas through a series of baffles while thegas is still at high pressure and low velocity. The entrained particleswill not follow the same path as the gas stream and they will impinge onthe walls and be trapped. 1

It should be noted that other azides beside-sodium azide may be used inthe compositions of this invention provided that the azide has a similarsensitivity to sodium azide. A specific azide which may be used islithium azide.

The conventional solid propellant ignitor which is used to initiatereaction need only be present in extremely small quantities because oncethe reaction is started it no longer requires th presence of theignitor. Any of the well known solid propellant ignitors can be used.Some examples of these'ignitors are black powder, pyrotechnics, metaloxident mixtures, such as horon/KNO aluminum/potassium perchlorate,thermites, etc. The exact nature of the ignitor is immaterial since itsonly function is to start the reaction. Thus the ignitor is a separatedevice which contains any of the art recognized solid propellantinitiatorsand which is either contained in or vented into the combustionchamber.

The general nature of the invention having been set forth, the followingexample is presented as aspecific illustration thereof. It will beunderstood that the invention is not limited to this example but issusceptible to various modifications that will be recognized by one ofordinary skill in the art.

EXAMPLE A 20 gram pellet of percent by weight NaN and 20 percent byweight S was prepared. About 2 grams of the standard solid rocketpropellant initiator, boron-KNO was ignited in the combustion chamber.The pellet was fired in a test chamber by igniting the conventionalignitor.

Other pellets which have been prepared comprise 1 60 percent by weightNa N percent by weight sulfur and 25 percent by weight Na CO and (2) 61percent by weight Na N 15 percent by weight sulfur and 24 percent byweight Ca CO Obviously, numerous modifications and variations of thepersent invention are possible in light of the above techniques. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

l. A solid, nitrogen generating composition consisting essentially of(1) an azide selected from the group consisting of sodium azide, lithiumazide and mixtures thereof and (2) sulfur.

2. The composition of claim 1 wherein said azide is sodium azide.

3. The composition of claim 1 which additionally contains a substance ormixture of substances which can produce C0 4. The composition of claim 3wherein said substance is a carbonate.

5. The composition of claim 1 wherein said azide and said sulfur arepresent in about stoichiometric quantities.

6. The composition of claim 3 wherein said azide and said sulfur arepresent in about stoichiometric quantities.

7. The composition of claim 1 wherein the quantity of either said azideor said sulfur is not less than about 20 percent of the stoichiometricquantity.

8. The composition of claim 3 wherein the quantity of either said azideor said sulfur is not less than about 20 percent of the stoichiometricquantity.

9. The composition of claim 1 wherein the quantity of said azide or saidsulfur is not less than about percent of the stoichiometric quantity.

10. The composition of claim 3 wherein the quantity of either sidesulfur or said azide is not less than about 75 percent of thestoichiometric quantity.

1 1. A method of generating hot nitrogen gas comprising igniting thecomposition of claim 1.

12. A method of generating hot nitrogen and CO comprising igniting thecomposition of claim 3.

13. A method of generating hot nitrogen which is capable of use in a gasdynamic laser comprising igniting the composition of claim 5.

14. A method of generating hot nitrogen and CO which is capable of usein a gas dynamic laser comprising igniting the composition of claim 6.

2. The composition of claim 1 wherein said azide is sodium azide.
 3. Thecomposition of claim 1 which additionally contains a substance ormixture of substances which can produce CO2.
 4. The composition of claim3 wherein said substance is a carbonate.
 5. The composition of claim 1wherein said azide and said sulfur are present in about stoichiometricquantities.
 6. The composition of claim 3 wherein said azide and saidsulfur are present in about stoichiometric quantities.
 7. Thecomposition of claim 1 wherein the quantity of either said azide or saidsulfur is not less than about 20 percent of the stoichiometric quantity.8. The composition of claim 3 wherein the quantity of either said azideor said sulfur is not less than about 20 percent of the stoichiometricquantity.
 9. The composition of claim 1 wherein the quantity of saidazide or said sulfur is not less than about 75 percent of thestoichiometric quantity.
 10. The composition of claim 3 wherein thequantity of either side sulfur or said azide is not less than about 75percent of the stoichiometric quantity.
 11. A method of generating hotnitrogen gas comprising igniting the composition of claim
 1. 12. Amethod of generating hot nitrogen and CO2 comprising igniting thecomposition of claim
 3. 13. A method of generating hot nitrogen which iscapable of use in a gas dynamic laser comprising igniting thecomposition of claim
 5. 14. A method of generating hot nitrogen and CO2which is capable of use in a gas dynamic laser comprising igniting thecomposition of claim 6.